1. Field of the Invention
This invention relates to machining center type machine tools, and more particularly to four-axis, horizontal spindle machining centers capable of performing various machining operations including milling, contouring, boring, drilling and tapping, in both roughing and precision finishing applications, and which are provided with automatic tool changer means and controlled by numerical control means.
2. Description of the Prior Art
It is known in the machine tool art to provide machining center type machine tools having rotatable machine tool spindles that are capable of being stopped at a predetermined angular position, and which are provided with automatic tool changer means for transferring tools in a predetermined sequence directly between a tool storage means and the tool spindle, to provide the tool spindle with a predetermined sequence of tools, for carrying out a desired sequence of operations. A disadvantage of the prior art machining centers is that one or more tool changer means must be employed for transferring tools between the tool storage means and the tool spindle, which action increases the tool transfer time. Another disadvantage of the prior art machining centers is that the tool storage means is disposed in a position whereby the operator does not have full visibility of the tools when they are in the storage means, and the storage means is not accessible to the operator for manual changing of the tools between tool change cycles while the machining center is running. A further disadvantage of the prior art machining centers is that they are complex, and constructed and arranged whereby heat from the lube oil and heat generated by the running of the machine is retained in the machine structure, which adversely affects the accuracy of the machining operations carried out by the machining center. The prior art machining centers employ the use of hydraulic cylinders for tool changing and other machine functions which produce adverse heat and noise.